Fonts on Alpine Linux covers a wide range of various languages. If you can't see your language, you need to install the font that has glyphs (little picture) created for it. The square box called a substitute character or "tofu" that acts as a placeholder for missing a glyph usually with a two byte sequence. Tofu is a food prepared in cubes and considered gross by some people.
Example how to install the font:
sudo apk add terminus-font
fc-cache -fv can be used to display the font locations and to update the cache. The system font directory is located at /usr/share/fonts which is reserved for the Alpine package creators and the package system. The user font location is located in ~/.font which is the preferred install font location especially from unknown sources. Fonts have been used as a source of security exploits (See CVEs) so to reduce the spread of attack install fonts inside ~/.font. The trusted system fonts that Alpine LInux packages typically are from well known sources like corporations like Google, Adobe, open organizations like XOrg or well known font designers or projects licensed as either SIL, GPL, etc.
If you install xorg-server, it will pull font-misc-misc meaning that many popular languages (Japanese, Korean, Latin, Cyrillic) are already covered except for Arabic, Persian, Thai, Tamil, etc from inspecting the Wikipedia Page left column on languages for article translation.
The default may be an eyesore so there are alternatives mentioned below.
Some applications do not specify a specific font to use but rather say sans-serif [sans means without as in without tiny lines], serif, monospace [as in proportional square font]. This is where Fontconfig comes into place by substituting the general font type with a specific font that you like. For package developers, /etc/fonts/conf.avail contains a fontconfig configuration file. This will be symlinked into /etc/fonts/conf.d. See /etc/fonts/conf.d/README for details about the meaning behind the priority numbers.
For regular users, you want to create/edit your personal ~/.fonts.conf. This is in XML and describes which preferred font to use for these general types. See this for details.
List of fonts in Alpine Linux
- Utopia - font-adobe-utopia-*
- Noto - font-noto-* -- These fonts can cover different glyphs for your language. If you go to https://www.google.com/get/noto/ , you can try to search for your language to see if it is supported. If Alpine doesn't have it, you can download it from Google into your ~/.font . As hinted in the introduction, noto comes from no tofu or gradual elimination of these substitute characters off the web.
font-noto font-noto-adlam font-noto-adlamunjoined font-noto-arabic font-noto-armenian font-noto-avestan font-noto-bamum font-noto-bengali font-noto-buhid font-noto-carian font-noto-chakma font-noto-cherokee font-noto-cypriot font-noto-deseret font-noto-devanagari (Hindi / Sanskrit) font-noto-emoji font-noto-ethiopic font-noto-extra font-noto-georgian font-noto-glagolitic font-noto-gothic font-noto-gujarati font-noto-gurmukhi font-noto-hebrew font-noto-kannada font-noto-kayahli font-noto-khmer font-noto-lao font-noto-lisu font-noto-malayalam font-noto-mandaic font-noto-myanmar font-noto-nko font-noto-olchiki font-noto-oldturkic font-noto-oriya font-noto-osage font-noto-osmanya font-noto-shavian font-noto-sinhala font-noto-tamil font-noto-telugu font-noto-thaana font-noto-thai font-noto-tibetan font-noto-tifinagh font-noto-vai
- Terminus - terminus-font -- Monospace font
- BaKoMa font-bakoma-* -- Fonts for TeX typesetting system (for academics in the math and sciences and book writers) and TeX (WYSIWYG) editors
- Bitstream Speedo - font-bitstream-speedo
- Bitstream Vera font-bitstream-*
- Bera (Bitstream Vera Type 1) - font-bitstream-type1 -- Use for LaTeX
- Ubuntu - ttf-ubuntu-font-family
- Font Awesome - ttf-font-awesome -- It was used in Twitter Bootstrap. It is a font representing things and brands as Icons.
- GNU FreeFont - ttf-freefont -- See link for support for different writing systems/languages
- GNU Unifont - unifont -- It contains glyphs of every codepoint
- font-misc-cyrillic -- Cyrillic fonts (Russian/Slavic Style)
- font-screen-cyrillic -- X.org public domain Cyrillic fonts for screen use
- font-misc-ethiopic -- Ethiopic fonts used in Ethiopia and Eritrea
- font-misc-meltho -- For the Syriac language
- font-misc-misc -- Bitmap fonts in PCF format (shows glyphs of many types and installed by default by xorg-server package)
- ClearlyU fonts - font-mutt-misc -- Thai, Ethiopic, Hebrew, Romanian, Persian, Korean Hangul, Greek, Persian, Russian/Slavic Cyrillic, Macedonian/Serbian, Armenian, Georgian, Lao, Devanagari, Urdu (Hindustani as in Northern India and Pakistan), Cherokee, Thaana. See link to changelog for full list of languages supported.
- tewi font font-tewi - A tiny bitmap font that contains braille glyphs
- Overpass - font-overpass
- Luxi fonts - font-bh-* -- designed by Kris Holmes and Charles Bigelow which bh is refers to the last name
- Lucida Typewriter - font-bh-lucidatypewriter-*
- IPA Font - font-ipa -- A Japanese font
- Chrome OS core fonts - font-croscore
- Vollkorn - font-vollkorn - A serif font with glyphs for Cyrillic (Russian/Slavic), Greek, Polish, Dutch, Bulgarian, Serbian, and small capitals
- Open Sans - ttf-opensans
- Cantarell - ttf-cantarell -- Designed for reading and the default GNOME font
- DejaVu - ttf-dejavu -- A modified Bitstream Vera with more styles and unicode coverage
- Linux Libertine - ttf-linux-libertine -- A free alternative to Times New Roman
- Liberation ttf-liberation -- A free alternative to Helvetica and Arial
- Inconsolata - ttf-inconsolata -- A monospace font designed for terminals and reading source code
- mononoki - ttf-mononoki -- A font for programming and code review
- Droid - ttf-droid / ttf-droid-nonlatin -- Designed for small screens and was used in older Android
- font-schumacher-misc -- Fixed width fonts by Dale Schumacher
- font-sony-misc -- Japanese Kana fonts by Sony Electronics
- font-daewoo-misc -- JIS (Japanese Industrial Standards) Kanji and Korean Hangul fonts by Daewoo Electronics
- font-cursor-misc -- A standard cursor font
- font-sun-misc -- Cursor and glyph fonts by Sun Microsystems
- font-winitzki-cyrillic -- A Cyrillic (Russian) font by Serge Winitzki designed for proofreading mixed Russian-English text
- font-isas-misc -- Chinese Song Ti style fonts (thinner horizontal lines compared to vertical)
- font-jis-misc -- A Japanese International Standard font
- IBM Courier font-ibm-type1
- font-dec-misc -- A Digital Equipment Corporation cursor and session fonts
- font-cronyx-cyrillic -- A Russian font for X11 by Cronyx
- font-arabic-misc -- A bitmap and proportional Arabic font in newspaper style 
- Core fonts for the Web msttcorefonts-installer-- For installing non-free proprietary Microsoft fonts like Comic Sans . Not recommended for commercial project or open source projects. See their licensing.
Andale Mono Arial Black Arial Comic Sans MS Courier New Georgia Impact Times New Roman Trebuchet Verdana Webdings